As an example using a comb teeth type actuator, there are ink jet printers. In case of this ink jet printer, an ink discharging part, as described in Japanese Patent Publication No. 5-246025A, has a plurality of nozzles which are aligned and allocated, ink chambers which contain ink to be discharged at the back part of each nozzle, and pressure generating members which comprise piezoelectric elements at positions opposite to respective nozzles. The ink chambers are pressurized and transformed by transformation of piezoelectric elements, so that ink droplets are discharged to flow. Pressure generating members as actuators are normally aligned and allocated in alignment with positions of the nozzles, and pressure generating members formed of comb teeth shape are utilized as actuators.
Then, in case that resolution of a printer is of 180 dpi, alignment pitch of nozzles becomes 141 μm, and pitch of neighboring actuators, i.e., pitch of comb teeth is also formed by this spacing. Therefore, refined and skilled dimensional precision is required, and an actuator which comprises such comb teeth shaped piezoelectric element is formed in a manner as shown in a manufacturing process chart of FIG. 6. In this manner, a plurality of piezoelectric material green sheets 21 on which electrode films 20 are formed are laminated and sintered to form a multi-layer piezo-actuator 22, and it is processed by a dicer etc. to form slits 23 and comb teeth 24. In addition, in FIG. 6, A shows a before laminating state, and B shows a pressurized and laminated state, and C shows a fired and integrated state, and D shows a state in which comb teeth are formed by carrying out a dicer process.
However, since the forming method in which slit fabrication is carried out by the above dicer etc. occurs after sintering of the piezoelectric material green sheet, corner portions tend to be easily dropped out and interlayer separation tends to easily occur, and in concrete terms, the following problems exists.
Firstly, residual stress occurs between a piezoelectric material layer and an electrode material layer, due to difference etc. of coefficient of thermal expansion of both materials. Therefore, since a surface thereof is exposed by machine work, an interlayer separation defect tends to easily occur during the machine working. Further, separation tends to occur between the piezoelectric material layer/electrode material layer at the worked surface during use.
Secondly, in the slit fabrication, since respective slits are formed by cutting off by the dicer etc., it takes a long amount of time to form the slits, even if they are formed at a dash by a plurality of dicer blades.
Thirdly, cleansing is necessary since it is contaminated by working fluid after the slit fabrication, but because strength after the fabrication is lower, cleansing—drying processes have to be carried out carefully, and at high costs.
Fourthly, there are design constraints. This means that slit width between comb teeth in a practical design is constrained by the thickness of the dicer blade for fabrication use and can not be, approximately, 70 μm and below. Therefore, it was not possible to obtain a comb teeth type actuator of higher density, or higher strength, or higher strength and higher output. Also, since only linear or planar slit fabrication is possible, when comb teeth of a complex shape is necessitated, there was no other choice than accommodating by adhering a component in post-process as described in, for example, Japanese Patent Publication 6-71877A.